Writing instrument

ABSTRACT

A writing instrument comprises a barrel for accommodating a writing body and a sleeve attached to an outer circumferential face of the barrel and made of an elastic soft material. A plurality of ribs extending in the axial direction are formed on the outer circumferential surface of the barrel, a groove fitted to the rib is formed on an inner circumferential surface of the sleeve, and a gap portion is formed between the adjacent ribs between the sleeve and the barrel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a writing instrument in which a sleeve made of an elastic soft material is attached at least at a gripping portion of a barrel for accommodating a writing body.

2. Description of the Related Art

Conventionally, various writing instruments, in which a sleeve formed in a cylindrical shape by an elastic resin material is attached to a gripping portion of a barrel have been proposed and sold in the market. Some of the writing instrument, in which the sleeve made of an elastic resin material is merely attached on the outer circumferential surface of the barrel depends for its elasticity only on the elastic characteristic of the sleeve itself when being gripped. Therefore, a problem is that a sufficient gripping force absorbing effect or gripping feeling improvement effect can not be obtained. Also, when the elastic resin material is hardened after long time of use, the effects are further deteriorated.

On the other hand, a writing instrument disclosed e.g. in the Japanese Utility Model Laid-Open No. 63-60375, has a plurality of projected ribs extending in the axial direction are formed on the inner circumferential surface of the sleeve and a projecting end of the projected rib is brought into contact with the outer circumferential surface of the barrel in order to improve gripping feeling. By this, a gap portion is formed between the inner circumferential surface of the sleeve and the outer circumferential surface of the barrel. Because of existence of this gap portion, the sleeve can be deformed to sink into the gap portion when the sleeve is gripped so that the gripping feeling is improved.

However, with the writing instrument in this gazette, a connecting force of the sleeve to the barrel is weak, and a problem is that the sleeve is easily moved relative to the barrel when it is gripped.

In response to the above-described problem, in the writing instrument disclosed in the Japanese Patent No. 3464791, a thickness of a peripheral wall of the sleeve is set to be large, a plurality of gap portions penetrating the peripheral wall in the axial direction are formed and the gap portions are arranged in the circumferential direction.

According to the writing instrument described in the above-described gazette, when the sleeve is gripped, the outer circumferential surface of the sleeve is elastically deformed easily by the existence of the plural gap portions in the sleeve peripheral wall, and moreover, deformation is not generated on the inner circumferential surface of the sleeve and thus, slip between the inner circumferential surface of the sleeve and the barrel outer circumferential surface is not caused.

However, even in the writing instrument in this gazette, the inner circumferential surface of the sleeve is merely in contact with the outer circumferential surface of the barrel, and the position is maintained merely by a frictional force of the sleeve, and therefore, a problem is that the slip of the sleeve with respect to the barrel can not be fully prevented.

SUMMARY OF THE INVENTION

In view of the foregoing and other drawbacks, disadvantages and problems of the conventional methods and structures, an object of the present invention is to provide a writing instrument which can improve gripping feeling of a sleeve without slip of the sleeve with respect to a barrel.

In order to achieve the above-described object, a writing instrument according to the present invention comprises a barrel for accommodating a writing body and a sleeve attached to the outer circumferential surface of the barrel and made of an elastic soft material, in which a plurality of first engaging portions extending in the axial direction and projecting in the direction of the inner diameter are provided on the inner circumferential surface of the sleeve, second engaging portions to be engaged with the first engaging portion is formed on the outer circumferential surface of the barrel, and a gap portion is formed between the adjacent first engaging portions between the sleeve and the barrel.

Mutual engagement between the first engaging portion formed on the sleeve and the second engaging portion formed on the barrel disables relative rotation of the sleeve with respect to the barrel. By this, slip of the sleeve in the rotating direction with respect to the barrel is prevented.

When a user grasps a gripping portion of the writing instrument, the sleeve can sink into the gap portion and be deformed, and the gripping feeling can be improved. Also, slip of fingers can be prevented by this deformation.

The outer profile shape of the cross section of the sleeve can be a non-circular polygonal shape including a triangle, and the above-described first engaging portion can be formed on the inner circumferential surface portion corresponding to an angle portion of the polygonal shape. The polygonal shape may be optional, but a triangular shape is advantageous since it corresponds to the number of commonly used gripping thumb and fingers. The above-described polygonal shape can be constituted by side portions and angle portions. The side portion has a small curvature but it does not have to be a straight line, while the angle portion has a large curvature but it does not have to be sharp.

The outer profile shape of the cross section of the sleeve can be varied according to the position in the axial direction. By this, different gripping feelings according to the gripping position in the axial direction can be obtained, and a user can choose the gripping position in the axial direction so that a favorite gripping feeling can be obtained.

The outer profile shape of the cross section of the sleeve can be varied so that the proportion shared by the side portion of the above-described polygonal shape is continuously increased from the front toward the rear. By this, different gripping feelings according to the position in the axial direction can be given to the user and moreover, design of the writing instrument can be improved.

The barrel can include a front barrel to which the above-described sleeve is attached and a rear barrel which is located in the rear of the front barrel, and the outer profile shape of the cross section of the above-described rear barrel can conform to the outer profile shape of the rear end of the above-described sleeve forming the non-circular polygonal shape of triangle or a shape with more than three angles. By this, the sleeve conforms to the portion of the barrel to which the sleeve is not attached and the design of the writing instrument can be improved.

A clip can be mounted to the rear barrel, and the clip can be mounted at the circumferential position aligning with one of the angle portions of the polygonal shape of the cross section of the sleeve and one of the angle portions of the polygonal shape of the cross section of the rear barrel.

It is preferable that the second engaging portion of the barrel projects from the outer circumferential surface of the barrel toward the outer diameter, and by this, the shape of the first engaging portion of the sleeve can be maintained by the second engaging portion and the shape of the gap portion can be supported by the second engaging portion of the barrel, which can prevent crush of the gap portion due to aged deterioration.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of preferred embodiments of the invention with reference to the drawings, in which:

FIG. 1 is a side view showing an embodiment of a writing instrument according to the present invention;

FIG. 2 is an overall vertical sectional view of the writing instrument in FIG. 1, but the internal structure is not shown;

FIG. 3 is a sectional view seen along 3-3 line in FIG. 1;

FIG. 4 is a sectional view seen along 4-4 line in FIG. 1; and

FIG. 5 is a view showing the use state of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described below referring to the drawings.

FIG. 1 is an overall view of a writing instrument, in which a writing instrument 10 is provided with a barrel 12. In this example, the barrel 12 is constituted by a plurality of parts of a front barrel 14, a rear barrel 16, a metal barrel ring 15 inserted between the front barrel 14 and the rear barrel 16, a tip member 18 to be connected to the tip end of the front barrel 14, and a tail plug 19 to be connected to the rear end of the rear barrel 16. However, not limited to this, the barrel 12 may be constituted by the arbitrary number of parts including one. Also, these plural parts are integrally connected or detachably connected as appropriate, if necessary. The front barrel 14 is constituted by a hard resin such as polymethylmethacrylate (PMMA) and ABS resin which is harder than a sleeve 20, which will be described later. The rear barrel 16 may be constituted by the same material as that for the front barrel 14.

In this embodiment, the front barrel 14 has an outer diameter smaller than the rear barrel 16. The cross section of the front barrel 14 corresponding at least to the gripping portion basically forms a circular outer profile, and a plurality (three, in this embodiment) of ribs 12 a are formed in the circumferential direction with an equal interval, projecting from this circular outer profile in the direction of the outer diameter and extending in the axial direction.

Inside the barrel 12, a writing body 30 allowing the instrument to function as a writing instrument and a mechanism for driving the writing body are accommodated, but since a publicly known mechanism can be applied, its detailed description is omitted.

The sleeve 20 made of an elastic soft material is attached to the outside of a portion of the barrel 12 corresponding at least to the gripping portion (particularly, the front barrel 14). The elastic soft material may be selected from a synthetic rubber, thermoplastic elastomer, soft synthetic resin or the like. The outer profile of the cross section of the sleeve 20 is not circular but a deformed triangle based on a triangle corresponding to the number of thumb and fingers usually used when gripping a writing instrument, that is, the thumb, the index finger and the middle finger. Specifically, the portion corresponding to each side of the outer profile of the triangle is a gentle side portion 20 a with a small curvature and the portion corresponding to each apex of the triangle is not acute but is an angle portion 20 b with a large curvature. All the angle portions 20 b are on the locus of a single circle with the axis of the barrel 12 as its center, and thus, the radius of curvature of the angle portions 20 b is the radius of the circle. On the other hand, the radius of curvature of the side portion 20 a is naturally larger than the radius of the circle. This outer profile shape is varied gradually from a circle to a deformed triangle from the front to the rear, in other words, the proportion shared by the side portions 20 a is gradually increased.

In the angle portions 20 b, a projection portion 20 c projecting in the direction of the inner diameter is formed on the inner circumferential side of the sleeve 20 in the axial direction, and a groove 20 d extending in the axial direction is formed on the projection portion 20 c. The groove 20 d has a dimension in which the rib 12 a of the above-described barrel 12 can fit.

The tip end of the sleeve 20 is in a tapered shape and fits in a recess portion 18 a formed at the tip member 18.

It is preferable that the outer profile of the rear barrel 16 is formed so that it continues to the outer profile of the sleeve 20, by which a feeling of integrity in design may be given as a whole. Specifically, the outer profile of the rear barrel 16 is gradually varied from a deformed triangle to a circle from the front to the rear. And as with the sleeve 20, a portion corresponding to each side of the outer profile of the triangle of the rear barrel 16 is a gentle side portion 16 a with a small curvature, while a portion corresponding to each apex of the triangle is not acute and forms an angle portion 16 b with a large curvature. A clip 22 is mounted to the rear barrel 16, and the circumferential position of the clip 22 aligns with the circumferential position of one of angle portions 16 b and one of the angle portions 20 a.

When attaching the sleeve 20 to the barrel 12, the tip end of the sleeve 20 is inserted into the recess portion 18 a of the tip member 18 and then, the front barrel 14 is inserted through the rear end of the sleeve 20. At this time, the rib 12 a is inserted in correspondence with the groove 20 d of the sleeve 20. And the tip end of the front barrel 14 is connected to the rear end of the tip member 18. By positioning the rib 12 a in the groove 20 d, the sleeve 20 can be easily assembled to the barrel 12.

In the writing instrument constituted as above-described, since the tip end of the sleeve 20 fits in the recess portion 18 a formed on the tip member 18 and the rear end of it is brought into contact with the metal barrel ring 15, it is positioned in the axial direction. Also, the groove 20 d on the inner circumferential surface of the sleeve 20 is fitted with the rib 12 a on the outer circumferential surface of the front barrel 14, and it is positioned in the circumferential direction. Therefore, the sleeve 20 is not rotated with respect to the barrel 12 or it does not slip, either.

Moreover, a gap portion 28 is formed between the sleeve 20 and the front barrel 14 between the adjacent ribs 12 a, 12 a.

Therefore, when a user is to use the writing instrument 10 and puts his fingers on the side portions 20 a of the sleeve 20 to grip it, the side portions 20 a sink into the gap portions 28 and are deformed as shown in FIG. 5, by which a gripping force is absorbed and gripping feeling can be improved. Deformation of the side portions 20 a also prevents slip of the fingers.

Since the adjacent side portions 20 a and the adjacent gap portions 28 are divided by the rib 12 a, the fingers are automatically guided by the side portions 20 a.

In this embodiment, if the axial position for gripping the sleeve 20 is changed, change of the shape of the sleeve 20 makes gripping feeling different since the size of the side portions 20 a is different depending on the axial position. Each user can write at any position where a desired gripping feeling can be obtained.

Since the ribs 12 a exist on the angle portions 20 b of the sleeve 20, the angle portions 20 b have a constitution which is hardly deformed as compared with the side portions 20 a. Therefore, if a user prefers gripping without cushion property, it is possible to write with the fingers in contact with the angle portions 20 b.

If the gap portions were defined by an elastic soft material as before, the rib portion or the projecting portion made of the elastic soft material would be deformed due to aged deterioration and the shape of the gap portion could not be maintained anymore, but according to the present embodiment, the projection portion 20 c of the sleeve 20 is reinforced by the hard rib 12 a to be engaged with the groove 20 d, and the shape maintaining capability is high. Also, a tension acts on the side portion 20 a of the sleeve 20 by the rib 12 a. Therefore, this allows the shape of the gap portion 28 to be maintained, and durability can be improved.

In the above-described embodiment, the sleeve is mainly attached on the outer circumferential surface of the front barrel, but the sleeve can be attached to the outer circumferential surface of an arbitrary portion of the barrel including the rear barrel. That is because the gripping portion is not necessarily limited to the front barrel portion but the rear of the barrel might be gripped depending on the user. Also, the cushion effect can be given not only to the finger tip but also to the palm holding the writing instrument.

Moreover, in the above-described embodiment, the grooves are formed on the sleeve and ribs are formed on the front barrel, but not limited to this constitution, an arbitrary engagement structure may be adopted. Also, grooves may be formed on the barrel and ribs may be formed on the sleeve.

While the invention has been described in terms of several preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. 

1. A writing instrument having a barrel for accommodating a writing body and a sleeve attached to an outer circumferential surface of the barrel and made of an elastic soft material, comprising: a plurality of first engaging portions provided on an inner circumferential surface of the sleeve extending in the axial direction and projecting in the direction of an inner diameter; second engaging portions to be engaged with said first engaging portion formed on the outer circumferential surface of the barrel; and a gap portion formed between said adjacent first engaging portions between the sleeve and the barrel.
 2. The writing instrument according to claim 1, wherein an outer profile shape of a cross section of said sleeve is a non-circular polygonal shape including a triangle or a shape with more than three angles in at least a part of a range in the axial direction, and said first engaging portion is formed on the inner circumferential surface portion corresponding to an angle portion of the polygonal shape.
 3. The writing instrument according to claim 2, wherein the outer profile shape of the cross section of said sleeve is a triangular shape.
 4. The writing instrument according to claim 2, wherein said sleeve has side portions and angle portions in said polygonal shape, the side portion has a small curvature and the angle portion has a large curvature.
 5. The writing instrument according to claim 1, wherein an outer profile shape of the cross section of said sleeve is varied according to the axial position at least in a part of a range in the axial direction.
 6. The writing instrument according to claim 4, wherein an outer profile shape of the cross section of said sleeve is varied so that the proportion shared by the side portions of said sleeve is continuously increased from the front to the rear.
 7. The writing instrument according to claim 2, wherein said barrel includes a front barrel to which said sleeve is attached and a rear barrel which is located in the rear of the front barrel, and an outer profile shape of a cross section of said rear barrel corresponds to the outer profile shape of a rear end of said sleeve forming a non-circular polygonal shape of triangle or a shape with more than three angles.
 8. The writing instrument according to claim 7, wherein a clip is mounted to the rear barrel, and the clip is mounted at a circumferential position aligning with one of the angle portions of the polygonal shape of the cross section of the sleeve and one of the angle portions of the polygonal shape of the cross section of the rear barrel.
 9. The writing instrument according to claim 1, wherein the second engaging portions of said barrel project from the outer circumferential surface of the barrel in the direction of an outer diameter.
 10. The writing instrument having a barrel and a sleeve attached to an outer circumferential surface of the barrel and made of an elastic soft material, wherein either one of a plurality of ribs and grooves extending in the axial direction is formed on an inner circumferential surface of the sleeve, the other of the ribs and the grooves to be fitted in either one of the ribs and the grooves is formed on the outer circumferential surface of the barrel, and a gap portion is formed between the adjacent ribs between the sleeve and the barrel.
 11. A method for providing a cushion effect to a writing instrument having a barrel and a sleeve attached to an outer circumferential surface of the barrel and made of an elastic soft material, comprising forming a plurality of first engaging portions on an inner circumferential surface of the sleeve extending in the axial direction and projecting in the direction of an inner diameter, forming second engaging portions engaged with said first engaging portions on the outer circumferential surface of the barrel, and forming a gap portion between said adjacent first engaging portions between the sleeve and the barrel. 